Transformer



Nov. 28, 1961 J. J. ANTALEK I'RANSFORMER 2 Sheets-Sheet 1 Filed Dec. 20,1957 INVENTOR. l/of/A/J A/TALEK Arroz/Jefe.

MI lllllll l 2 Sheets-Sheet 2 INVENTOR. L/o/A/ J JA/TALE( BY 777mm),/MW/ {MMM/M2M ,4 from/@s Nov. 28, 1961 J. J. ANTALEK TRANSFORMR FiledDec. 20, 1957 windings.

United States Patent O 3,011,138 TRANSFORMER John'J. Antalek, Chicago,Ill., assignor to Radio Industries, Inc., Chicago, Ill., a corporationof Illinois Filed Dec. 20, 1957, Ser. No. 704,119 1 Claim. (C1. 336-87)The present invention relates to transformers and more particularly toIF transformers having adjustable couplingy between the primary andsecondary windings thereof.

There are many applications, including the output IF stage of a signalseeking receiver, which require the use of high frequency transformershaving between the primary and secondary windings thereof a mutualcoupling which is adjustable with a high degree of precision. In suchapplications it i-s usually important that the adjustment of the mutualcoupling of the transformer have a negligible effect on the respectiveinductance values of the windings and thus on the center `frequencies ofthe primary and secondary windings and their associated tuned circuitcomponents.

Therefore, a principal object of the present invention is to provide anew and improved high frequency transformer haiving a mutual couplingwhich is adjustable to precise values within a relatively wide range,and which may be manufactured at a relatively low cost.

Another object of the present invention is to provide a new and improvedhigh frequency transformer including means for adjusting the mutualcoupling between a primary and a secondary winding thereof withoutapprecik ably changing the center frequency of either the input orOutput tuned circuits of the transformer.

A further object of the present invention is to provideL vide a new andimproved highy frequency transformer including means for adjusting thebandwidth of the trans former throughout a relatively wide range.

Another object of the present invention is to provide new and improvedmeans for adjusting thegain of a high frequency transformer withoutappreciably changing the Q thereof.

Another object of the present invention is to provide means foradjusting the Q of a transformer without appreciably affecting the gainthereof.

Another object of the present invention is to provide a new and improvedhigh frequency transformer construction. s

Very briefly, the above and further objects are realized in accordancewith the present invention by providing a high frequency transformerwhich includes primary and secondary windings spatially wound von acommon coil form in which a pair of tuning cores are threadedlysupported for respectively adjusting the inductances of the The coilform is disposed within a conductive shielding can and mounted on aninsulating base to which the can is attached, and a mutual couplingadjusting means is mounted in the can for transverse movement betweenthe transformer windings.

The invention, .both as to its or'ganizationand operation, together withfurther objects and advantages thereof, will best be understood byreference to the following detailed description taken in connection withthe accompanying drawings, in which:

FIG. 1 is an isometric View of a high frequency transformer embodyingcertain features of the present invention; f

FIG. 2 is a sectional view taken along the line 2-2of FiG. l; i

i terminals.

FIG. 3 is a sectional view of the transformer of FIG. 2 taken along theline 3-*3 thereof, assuming the entire structure to be shown therein;

FIG. 4 isa sectional view taken along the line 4-4 of FIG. 2, assumingthe entire structure to be shown therein;

FIG. 5 is a sectional View taken along the line 5-5 of FIG. 2,y assumingthe entire structure to be shown therein;

FIG. 6 is an exploded isometric View of the base portion of thetransformer of FIG. l;

FIG. 7 is a fragmentary sectional view taken along the line 7-7 of FIG.2, assuming the entire structure to be Shown therein;

FIG. 8 is a fragmentary exploded perspective view showing thearrangement used for mounting terminal members in the support base ofthe transformer of FIG. l;

FIG.y 9 is a cross sectional view similar to FIG. 4 showing anotherfeature of the present invention;

FIGS. 10 and 1l are respective top and bottom views of a multiplecapacitance device employed in the transformer illustrated in FIG. l;and

FIG. l2 is a circuit diagram of the transformer of FIG. l.

Referring now to the drawings and particularly to FIGS. 1-5, there isshown an IF type high frequency transformer 10 comprising a generallyrectangular insulating base 11 on which are mounted a plurality ofterminal members 12, 1 3, 14, 15, 16 and 17, and a rectangular shieldingcan or housing 18.

As best shown in FIG. 6, the base 11 is substantially square in crosssection and includes a plurality of terminal mounting receptacles 21arranged along opposite side edges thereof. The receptacles 21 arearranged in two sets of three and, therefore, the terminals 12-17 aresimilarly arranged in two sets of three. The terminals'12-17, which aresubstantially identical, are punched and stamped from a sheet ofsuitable conductive metal and each comprises an opstanding slightlyangulated connector portion 22 having a notch 23 provided near the upperend thereof for facilitating connection thereto of one of the lead-sfrom the transformer windings. A perpendicularly disposed offset tab 24is provided adjacent to and directly beneath the upstanding portion 22for operative engagement with the upper surface of the base 11 ytoprevent withdrawal of the terminal through the receptacle from thebottorn'of the base 11 and to provide an electrical connection betweenthe terminal and a capacitor element mounted on the base 11 anddescribed in greater detail hereinafter'. The portion of each terminalwhich extends into the receptacle 21 includes a tapered or necked-downportion -26 which connects an upper rectangular portion 25 disposedimmediately beneath the tab 24 with a lower rectangular portion 27 whichdepends from the base 11. The receptacles 21 each include an upperrectangularpo'rtion 31 (best shown in FIG. 8) having a widthsubstantially equal to the corresponding width of the upper terminalportion 25 and a tapered shoulder 32 connecting the portion`31 with thewalls of an aperture 41 at the bottom of the receptacle.`

In order to enable a rapid and facile assembly ofthe terminals 12-17 tothe basemember 11, the receptacles 21 are provided with an upper ormouth portion which is appreciably larger than the correspondingdimensions ofthe lower portions 27 of the terminals.' Moreover, certainones of the walls defining the receptacles v21 are tapered to lead theupper portions 25 of the terminals 1217 into those portions of thereceptacles which correspond in configuration to the upper portions 25of the portion partially defined by the walls 38 (FIGLS) whichConsidering the shape of the receptacles 21Vl in greater detail, eachreceptacle has an outer auxiliary 3 part by the walls 31. The receptaclewalls 38 are spaced apart by a distance slightly exceeding the width ofthe lower terminal portion 27 so that the lower convex end 37 of theterminals may fit in either the auxiliary or principal poltions of thereceptacle. Should the terminal end 37 initially move into the auxiliaryportion of the receptacle it rides down -a sloping cam surface 36 whichleads into an aperture 41 at the bottom of the principal receptacleportion thereby to move the terminal inwardly toward the m-ain terminalportion. In addition, the principal receptacle portion is provided witha bevel 35 at the inner upper end to further simplify insertion of theterminals into the receptacles.

The depending portions 27 of the terminals each include an elongatedaperture or slot 33' for facilitating connection of the transformer tothe circuits of the associated equipment, and the portions 27 alsocomprise an undercut portion 34 which may be used for facilitating thephysical wiring of the transformer in associated equipment.

In order to provide a self-contained IF transformer including thenecessary capacitances for tuning the primary and secondary windingsthereof, a plurality of capacitors are mounted internally of the unitbetween appropriate ones of the terminals 12-17. As best shown in FIGS.10 and l1, these capacitances are established between a plurality ofconductive layers 42, 43 and 44 disposed on the upper surface of a thininsulating member 45 and a plurality of conductive layers 46, 47 and 48disposed on the opposite and lower surface of the member 42. The lowerlayers or capacitor plates 46, 47 and 48 are respectively engaged by thetabs 24 on the terminals 13, and 17 and the upper plates 42, 43 and 44are engaged by the tabs 24 on the terminals 12, 14 and 16. The latterterminals thus hold the member 45 in place on the base 11 above the tabs24 on the terminals 13, 15 and 17. Capacitances are thus respectivelyprovided between the terminals 12 and 15, 14 and 17, 16 and 17, and 13and 16, the electric circuit of the transformer 10 being illustrated inschematic form in FIG. l2. It will be understood that differentconfigurations of the conductive layers on the sheet 45 may be used toprovide different capacitive circuit arrangements between the terminals12-17.

The terminals 1247 and the member 45 are secured to the base 11 by aneyelet 50 which extends through respective apertures 51 and S2 in thebase 11 and in the member 45. In order to insure a tight fit and thusgoed electrical connections between the terminals 12417 and the member45, the eyelet 58 extends through an apertured insulating block 53 andan apertured spring 54. Assembly of the base assembly is facilitated bya pair of upstanding flanges 55 on the base member 11 which insuresalignment of the apertures in the members 11, 45, 53 and 54 prior to theinsertion therethrough of the eyelet 50'. As shown, the eyelet 58comprises a head 56 in the form of an external flange which is receivedin a counterbore 57 at the bottom of the base 11, and the upper end ofthe eyelet 56 is peened over to at least partially compress the spring54and to fasten the base assembly together.

As best shown in FIGS. 2 and 3, the head 56 of the eyelet is formed by apartial toroidal portion including the outwardly extending flange whichseats in the counterbore 57 andan inwardly directed portion whichprovides a Seat 58 against which the lower end of a cylindrical coilformv 69 abuts. A pair of coils or transformer windings 71 and 72 arewound around the form69 at spaced apart locations and the ends of thesewindings are respectively connected to the terminals 12, 14, 15 and ,17.The 4wire- 'fromwhich the coils 71 and 72 are wound is very thin andfrangible, and breaking of the connec- I is prevented by means of aplurality of knurls 68 in the eyelet 50 which grip the form 69. The coilform 69 is formed of a resilient plastic so that as it is forced intothe eyelet 50 against the seat 58, the knurls 68 press into the form 69thereby to prevent relative rotation between the coil form 69 and thebase member 11.

As best shown in FIGS. 2 and 3, the transformer windings 71 and 72 arewound at spaced apart locations on the coil form 69 and are preventedfrom moving along the `form by a plurality of small protuberances 74which are integral with the form 69.

The shielding can 18, which is rectangular in cross section, tits snuglyover the base member 11. Two sets of ears 77 and 78 on the base member11 seat in notches 79 and 80 in the bottom of the can 18, and a pair ofstruck-out tabs 82 on the can 1S are bent into a pair of notches 83 onthe lower surface of the base member 11 to force the ears 77, 78 intothe bottoms of the notches 79 and 80. The shielding can is thus attachedto the base member 11.

In order to xedly mount the coil form 69 centrally of the shielding can18, a truste-conical upstanding sleeve 87 is provided at the center ofthe can 1S at the upper end thereof, and the coil form 69 extendspartially into this sleeve. The external diameter of the coil form 69has a dimension which is intermediate that of the internal diameters ofthe top and bottom of the sleeve 87, and since the coil form 69 isresilient, as the can 18 is pressed over the base member 11, the coilform 69 is press fitted into the sleeve 87. Accordingly, the coil form-69 is tightly held at the top and bottom to prevent relative movementbetween it and the shielding can 18.

The aperture 88 permits the use of a screw driver for adjusting a tuningslug or core 89 which is threadedly received in the upper portion of thecoil form 69 for adjustable movement into the winding 71. A similar core91 is disposed in the bottom of the core form 69 in proximity to thewinding 72 and may be adjusted `by means of a suitable tool such as ascrew driver insertable through the eyelet 50. The manner in which thetuning cores 89 and 91 are mounted within the coil form 69 is describedin detail in my copending application, Serial No. 520,332, led July 6,1955.

In order to enable adjustment of the mutual coupling between thetransformer windings 71 and 72 without appreciably affecting therespective inductances of these windings, there is provided inaccordance with the present invention an adjustable tuningmechanism 93mounted in the shielding can -18 transversely of the principal axis ofthe coil form 69. In the embodiment of the invention illustrated in FIG.4, the adjustable tuning mechanism 93 comprises a non-magnetic tube orsleeve 94 which is secured Aby suitable means in apertures 95 and 96 atopposite sides of Ithe can 18. Preferably, the sleeve 94 is formed ofplastic `and the ends thereof are turned over so as to stake the sleeve94 in place. \As best shown in FIGS. 2 .and 3, the apertures 95 and 96are positioned in the shield 18 so that when the transformer v10 isassembled, the tube 94 is approximately midway between the transformerwindings 71 `and 72 and extends partially within an imaginarycylindrical envelope defined by the outer turns of the windings 71 and72. In the embodiment of the invention illustrated in FIG. 4, a pair oftuning slugs or coresv 98 and 99 are respectively threaded into the tube94 from the oppositeV ends thereof and screw driver slots 98 and 99' inthe outer ends of the slugs 93 and 99 enable separate adjustment of thecores 98 and 99 to adjust the mutual coupling -between the windings 71`and 72 by movement of the cores into and out of the space directlybetween the windings 71 and 72 thereby to alter the magnetic field whichcouples the windings 71 and 72 together. The cores 98 and 99 arepreferably mounted in the sleeve 94 in the same manner as the cores 89and 91 are mounted in the coil form 69. f

Although two tuning cores 98 and 99 are employed' in the device of"IFIG. 4 for purposes more fully explained below, it will be apparent tothose skilled in the art that a single core may be used to adjust themutual coupling of the transformer. However, if but one core is used,the range of adjustment is less than where two cores of differentmagnetic characteristics are used, and the types of material chosen forthe cores 98 and 99 depend upon the desirability of having othercharacteristics of the transformer affected by the adjustment of themutual coupling thereof.

The data listed in Table I shows the changes in gain, Q, and bandwidthwhich were provided between the fully in and fully out positions oftuning cores of different materials when a transformer embodying thepresent invention was driven with a 265 kc. signal. yIn all cases, thevariation in center frequency was less than :15 kc.

From Table I it will be yapparent that a maximum change in bandwidthwith a constant transformer gain is provided when a brass core is used.However, where a much greater change in bandwidth is required, and asmall change in gain throughout the range of adjustment can betolerated, the use of two tuning cores, one of brass and one of RFpowdered iron may be employed, thereby doubling the change in bandwidthof the transformer. Accordingly, where a maximum adjustability ofbandwidth is desired the core 98 may be formed of brass and tthe core 99may be formed of RF powdered iron.

Referring to FIG. 9, there is shown Ia preferred embodiment of theinvention employing a single core 101 threadedly mounted in the tube 94..The core 1011 is a composite member =having end portions 102 and 1103secured together end to end along a line 104. The portion 102 may bebrass and the portion 103 may be RF powdered iron so as to provide atransformer having a maximum degree of bandwidth adjustability. Sincethe end portions 102 `and 103 are bonded together, as the core 101 ismoved through the tube 94 to move one portion thereof into the spacebetween the transformer windings 71 yand 72, the other portion of thecore -1011 is moved out of this space. Reference to Table I shows thatthe composite core `101 inthe transformer of FIG. 9 provides a bandwidthadjustment of 1 kc. with a change in gain of slightly more thanpercent.. Consequently,

only a single adjustable element is provided to control the bandwidth ofthe transformer throughout a wide range.

The characteristics of a transformer built in accordance with theembodiment of the invention illustrated in FIG. 9 are listed in TableII.

While particular embodiments of the invention have been shown, it willbe understood, of course, that the invention is not limited thereto,since many modifications may be made, and it is therefore contemplatedby the appended claim to cover any such modifications as fall yWithinthe true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

A transformer construction comprising an insulating base, an elongatedshield mounted on said base, a generally tubular coil form mounted onsaid base and extending upwardly therefrom into said shield, first andsecond coils mounted on said coil form with their axes extendinggenerally parallel to the axes of said tubular coil form, said first andsecond coils being spaced from each other along the axis of said form,first and second magnetic cores movably mounted in said coil form andeach positioned adjacent one of said first yand second coils, said baseand said housing each having an opening aligned with said coil form topermit adjustment of said irst and second cores, a nonmagnetic sleeveextending transverse to the axis of said coil form and located adjacentsaid coil form in a position between said rst and second coils, saidshield having a pairfof aligned openings fand said sleeve being disposedwithin said shield and mounted in said openings, and magnetic meansmovably mounted in Said sleeve and adjustable through said sleeve tovary the field coupling between said iirst and second coils.

References Cited in the file of this patent UNITED STATES PATENTS1,690,228 Heising Nov. 6, 1928 2,283,924 Harvey May 26, 1942 2,283,926Harvey May 26, 1942 2,343,101 Vogt Feb. 29, 1944 2,450,192 Freeman Sept.28, 1948 2,483,994 Davis Oct. 4, 1949 2,614,164 Huston Oct. 14, 19522,728,052 Van Duyne Dec. 20, 1955 2,753,532 Ashby July 3, 1956

